Flip chip with solder pre-plated leadframe including locating holes

ABSTRACT

A flip-chip with a solder pre-plated leadframe that includes locating holes. The leadframe does not include a die attach pad. Two of the leads include a locating or alignment hole for receiving a solder bump of the bumped die. The remaining leads include die contact areas for placement of the die thereon with the solder bumps contacting the die contact areas. The leads with the die contact areas are downset. The downset is approximately 4 mm.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to flip chips with solder pre-plated leadframes, and more particularly, to a flip chip with a solder pre-plated leadframe that includes locating holes for alignment.

2. Description of the Prior Art

The trend of miniaturizing packaging of semiconductor devices is driving the need to package a larger die in smaller packages. Current gold wire bond design rules limit die size to approximately 50% to 65% of the smallest dimension of the body size. Extra space is required to create a die attach area, space between the die attach area and wire bondable leads. The space prevents shorting between the die attach area and the leads. In addition, it provides some flexibility to loop the gold wire and form a reliable connection between the bond area and the bondable leads.

Methods have been developed for placing the flipped chip or “die” directly on the leadframe wherein the leadframe includes leads directly coupled to the die attach pad, thus eliminating the need for the gold wire. The chip connection to the frame is done with solder paste that is placed on the die attach pad prior to chip attachment to the frame. The solder paste is intended to hold the chip in place after the chip is attached to the frame. The eutectic solder paste will also make connection between high lead bumps on the chip to the frame. However, there are problems with this technology in handling the leadframe and the die thereon prior to reflowing the solder paste and placing the mold around the leadframe. The process window at the holding station must be controlled in order to avoid any shifting of the die. The process control and mold compound variations sometimes create a shifted die which results in opens and shorts, which thus result in a rejection of the final semiconductor. This is detrimental to the overall manufacturing yield.

SUMMARY OF THE INVENTION

The present invention provides a semiconductor device that includes a leadframe having a plurality of leads. The leadframe includes at least two alignment holes. The semiconductor device further includes a die coupled to the leadframe with solder. The alignment holes help ensure that the die remains properly positioned on the leadframe prior to the solder reflow that attaches the die to the leadframe.

In accordance with one aspect of the present invention, the leads include down set areas for receiving solder balls for coupling the die thereto.

In accordance with another aspect of the present invention, the down set is 4 mils.

The present invention also provides a method for manufacturing a semiconductor device. The method includes providing a wafer, placing solder bumps on the wafer and dicing the wafer. The resulting die is then attached to a plurality of leads that are coupled together. The die attach takes place at a heating station in order to reflow the solder bumps to solder pre-plated leads. Additionally, at least two of the leads include locating holes for receiving solder bumps and thereby properly positioning the die. Plastic molding is placed around the resulting die and coupled leads and the leads are then trimmed and formed and separated from one another.

Other features and advantages of the present invention will be understood upon reading and understanding the detailed description of the preferred exemplary embodiments, found hereinbelow in conjunction with reference to the drawings in which like numerals represent like elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an end view of a semiconductor device in accordance with the present invention;

FIG. 2 is a side sectional view of a semiconductor device in accordance with the present invention;

FIG. 3 is a bottom elevation view of a semiconductor device in accordance with the present invention; and

FIG. 4 is a top elevation view of a semiconductor device in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS

FIG. 1 illustrates a semiconductor device 10 including a die 11, and a plurality of leads 12. As can be seen in FIG. 1, the semiconductor device also includes an encapsulating body 13.

The semiconductor device is manufactured by providing a silicon wafer that is standard in the industry. A plurality of solder bumps 14 are arranged on the wafer and the wafer is diced to create a plurality of what are referred to in the industry as “bumped dies.” Thus, die 11 is preferably a bumped die.

A leadframe 15 is provided that does not include a die attach pad area. Thus, the leads are somehow coupled to one another. Preferably, they are coupled to one another at their distal ends 20. At least two of the leads include locating or alignment holes 21. The two leads may be on the same side of the leadframe, as illustrated in FIGS. 2 and 3. Alternatively, they may be in opposite comers from each other, or all four end or corner leads may include locating holes. Preferably, the holes are 100 microns or approximately the same size as the solder bumps. The leads without locating holes include solder bump contact areas 22.

The bumped die is placed on the leadframe such that two solder bumps are placed within the corresponding locating holes of the leads. This helps assure proper orientation of the die and helps ensure that it does not move during the remaining manufacturing process.

The solder bumps are then reflowed in order to couple the die to the leadframe. Preferably, the leads are solder pre-plated to help ensure a good connection. Preferably, the placement of the die on the leadframe takes place at a heating station so that the solder bumps may be reflowed thereby.

Molding, preferably made of plastic, is then placed around the coupled die and leadframe, thereby forming body 13. The leads are then trimmed and formed to separate the leads and to provide the resulting shape illustrated in FIG. 1.

As can be seen in FIGS. 1 and 2, preferably the leads have a downset on which the solder bumps rest. This helps prevent solder collapse and helps to maintain a steady distance between the leadframe and the die. Preferably, the downset is approximately 4 mils. As can been seen in FIG. 2, the leads that have the locating holes defined therein do not have the downset, thus allowing the solder bumps to go into the locating holes. However, the leads with locating holes do preferably include a platform 12 a for supporting the solder bumps. The platforms 12 a are substantially coplanar with solder bump contact areas 22. Preferably, the platforms also have a downset. In a preferred embodiment, the bump and lead pitch may vary from 0.5 mm to 0.75 mm.

FIG. 3 illustrates a semiconductor device 10 in accordance with the present invention from the bottom. Thus, platforms 12 a and solder bump contact areas 22 are visible. The illustration is primarily schematic and thus, does not reflect the bends within the leads 12.

Thus, the present invention allows a packaging die size up to 85% of the package body size. The locating holes help ensure that the die is properly oriented and that it remains properly oriented during the manufacturing process. Additionally, by directly coupling the die to leads and eliminating the gold wire bond technology, manufacturing cost is reduced and productivity is improved.

Although the invention has been described with reference to specific exemplary embodiments, it will appreciated that it is intended to cover all modifications and equivalents within the scope of the appended claims. 

What is claimed is:
 1. A semiconductor device comprising: a leadframe comprising a plurality of leads, each lead including a solder bump contact area, and at least two of the solder bump contact areas including an alignment hole defined within the corresponding leads and a platform underneath the solder bump contact area; a die; and a plurality of solder bumps, each solder bump contacting a respective solder bump contact area and the die; wherein the solder bumps that contact the solder bump contact areas that include an alignment hole are within the alignment hole.
 2. A semiconductor device in accordance with claim 1 wherein at least the solder bump contact areas are pre-plated with solder.
 3. A semiconductor device in accordance with claim 1 wherein the solder bump contact areas that do not include alignment holes are down set with respect to the solder bump contact areas that include alignment holes and are substantially coplanar with the platforms.
 4. A semiconductor device comprising: a leadframe comprising a plurality of leads, each lead including a solder bump contact area, at least two of the solder bump contact areas including an alignment hole defined within the corresponding leads and a platform underneath the solder bump contact area, and at least the solder bump contact areas being pre-plated with solder; a die; and a plurality of solder bumps, each solder bump contacting a respective solder bump contact area and the die; wherein the solder bumps that contact the solder bump contact areas that include an alignment hole are within the alignment hole; and wherein the solder bump contact areas that do not include alignment holes are down set with respect to the solder bump contact areas that include alignment holes and are substantially coplanar with the platforms.
 5. A semiconductor device comprising: a leadframe comprising a plurality of leads, each lead including a die contact area, at least two of the die contact areas including an alignment hole and at least the die contact areas being pre-plated with solder; a die; and a plurality of solder bumps, each solder bump contacting a respective die contact area and the die; wherein the solder bumps that contact the die contact areas that include an alignment hole are within the alignment hole; and wherein the die contact areas that do not include alignment holes are down set with respect to the die contact areas that include alignment holes.
 6. A semiconductor device in accordance with claim 5 wherein the downset is 4 mm. 